Pontoon boats are a popular watercraft, and making the pontoons for them has been accomplished by several methods. Whichever method of making a pontoon is used, a pontoon will generally have a straight central portion that comprises most of the length of the pontoon, an end cap that will be a blunt cap attached to the back end of the central portion, and a tapered portion forming a nose cone attached to the front end of the central portion that cuts the water as the boat moves forward. A former method for making pontoons consisted of roll forming short pieces of sheet metal laterally to make short cylinders, and welding a number of short cylinders to make a central portion. In so doing, a number of circumferential welds were produced where each cylinder was welded to an adjacent cylinder. In addition to the welds in the central portion, the end cap and nose cone also require circumferential welds. All of the circumferential welds are potential leak points. If a weld is incomplete or has porosity, water can enter the interior of the pontoon. The circumferential welds also add drag since they are raised relative to the smooth portions of the pontoon.
A more advanced method of making pontoons having fewer circumferential welds is disclosed in U.S. Pat. No. 6,644,229. In this patent, a single piece of sheet metal is inserted into rollers and rolled laterally to form a cylindrical central portion. The central portion made by this method has no circumferential welds between its ends. The length of the cylindrical central portion formed in this process is limited to the width of the rollers. The shape of the central portion produced is also limited to a circular or oval shape due to the configuration of the rollers. Another drawback to this process is that the rollers will bow outward during the rolling process, and the bowing is greater in proportion to longer lengths of the rollers. When the rollers bow, this will produce a central portion that is slightly bowed, which is detrimental to the performance of the pontoon in the water. Ideally a pontoon would be straight along its length and have no circumferential welds below the waterline.